EC Number   |
|---|
   4.1.2.48 | - |
| 4.1.2.48 | at 2.2 A resolution, in the unliganded form and cocrystallized with L-serine and L-threonine. No active site catalytic residue is revealed, and a structural water molecule is assumed to act as the catalytic base in the retro-aldol cleavage reaction. The very large active site opening suggests that much larger molecules than L-threonine isomers may be easily accommodated |
| 4.1.2.48 | hanging drop vapor diffusion, low-pH crystal structure of the enzyme at 2.1 A resolution, with a noncovalently bound uncleaved L-serine substrate, and a pyridoxal 5'-phosphate cofactor bound as an internal aldimine. This structure contrasts with other Escherichia coli L-threonine aldolase structures obtained at physiological pH that show products or substrates bound as pyridoxal 5'-phosphate-external aldimines. The non-productive binding at low-pH is due to an unusual substrate serine binding orientation in which the alpha-amino group and carboxylate group are in the wrong positions (relative to the active site residues) as a result of protonation of the alpha-amino group of the serine, as well as the active site histidines, His83 and His126. Protonation of these residues prevent the characteristic nucleophilic attack of the alpha-amino group of substrate serine on C4' of pyridoxal 5'-phosphate to form the external aldimine. At low pH the change in charge distribution at the active site can result in substrates binding in a non-productive orientation |
| 4.1.2.48 | the crystal structure of the low-specificity L-threonine aldolase is determined at 2.2 A resolution, in the unliganded form and co-crystallized with L-serine and L-threonine |
